A web offset printing press typically includes a plate cylinder, a blanket cylinder and an impression cylinder supported for rotation in the press. The plate cylinder carries a printing plate having a rigid surface defining an image to be printed. The blanket cylinder carries a printing blanket having a flexible surface which contacts the printing plate at a nip between the plate cylinder and the blanket cylinder. A web to be printed moves through a nip between the blanket cylinder and the impression cylinder. Ink is applied to the surface of the printing plate on the plate cylinder. An inked image is picked up by the printing blanket at the nip between the blanket cylinder and the plate cylinder, and is transferred from the printing blanket to the web at the nip between the blanket cylinder and the impression cylinder. The impression cylinder can be another blanket cylinder for printing on the opposite side of the web.
A conventional printing blanket is manufactured as a flat sheet. Such a printing blanket is mounted on a blanket cylinder by wrapping the sheet around the blanket cylinder and by attaching the opposite ends of the sheet to the blanket cylinder in an axially extending gap in the blanket cylinder. The adjoining opposite ends of the sheet define a gap extending axially along the length of the printing blanket. The gap moves through the nip between the blanket cylinder and the plate cylinder, and also moves through the nip between the blanket cylinder and the impression cylinder, each time the blanket cylinder rotates.
When the leading and trailing edges of the gap at the printing blanket move through the nip between the blanket cylinder and an adjacent cylinder, pressure between the blanket cylinder and the adjacent cylinder is relieved and established, respectively. The repeated relieving and establishing of pressure at the gap causes vibrations and shock loads in the cylinders and throughout the printing press. Such vibrations and shock loads detrimentally affect print quality. For example, at the time that the gap relieves and establishes pressure at the nip between the blanket cylinder and the plate cylinder, printing may be taking place on the web moving through the nip between the blanket cylinder and the impression cylinder. Any movement of the blanket cylinder or the printing blanket caused by the relieving and establishing of pressure at that time can smear the image which is transferred from the printing blanket to the web. Likewise, when the gap in the printing blanket moves through the nip between the blanket cylinder and the impression cylinder, an image being picked up from the printing plate by the printing blanket at the other nip can be smeared. The result of the vibrations and shock loads caused by the gap in the printing blanket has been an undesirably low limit to the speed at which printing presses can be run with acceptable print quality.
In response to these deficiencies in conventional flat printing blankets, gapless tubular printing blankets were developed by the assignee of the present invention. These gapless tubular printing blankets are described, for example, in U.S. Pat. Nos. 5,768,990, 5,553,541, 5,440,981, 5,429,048, 5,323,702, and 5,304,267.
In this regard, U.S. Pat. No. 5,304,267 is directed to a method of manufacturing a gapless tubular printing blanket. The specification of this patent describes a preferred method of manufacturing a gapless tubular printing blanket as "coating a compressible thread with a mixture of rubber cement and microspheres, and wrapping the coated thread in a helix around the cylindrical sleeve" to form a compressible layer; "coating an inextensible thread with a rubber cement that does not contain microspheres, and wrapping the coated thread in a helix around the underlying compressible layer" to form an inextensible layer, and "wrapping an unvulcanized elastomer over the inextensible layer, securing it with tape" and vulcanizing "the taped structure . . . so that a continuous seamless tubular form is taken by the overlying layers of elastomeric material. " Additional methods of manufacture are also described, including the manufacture of a gapless tubular printing blanket having a circumferentially inextensible sublayer comprising a continuous piece of plastic film extending in a spiral through the elastomeric material of an inextensible layer and around a compressible layer. The plastic film preferably has a width approximately equal to the length of the tubular printing blanket, and a thickness of only 0.001 inches so that the narrow seam defined by the 0.001 inch wide edge of the uppermost layer thereof will not disrupt the smooth, continuous cylindrical contour of an overlying printing layer.
DE 197 20 549 A1 purports to describe a method for manufacturing a cylinder carrier by winding of a continuous strip onto a supporting mandrel surface. The strip is unwound from a spool which is mounted so that it can pivot so that the strip winding angle is self adjustable. Strip tension is maintained during the winding process. Preliminary conditioning treatment and coating of the strip with an adhesive takes place between unwinding and winding of the strip. The preliminary treatment stations are mounted on a support wall which is installed to that it can pivot relative to the cylinder surface. The cylindrical carrier shell is coated with an integral layer of plastic material. The carrier shell is shown as having a fixed length.